LOOK who’s rediscovered the free market: Mayor Mike still embraces price caps on such things as apartments and taxi fares – but when it comes to Midtown’s streets, he now touts the virtues of charging a “fee” for this “limited commodity.” He calls it “congestion pricing.”

What woke up the billionaire-mayor? Well, guess who owns road rights – and who’d get to keep those fees?

Yup: City Hall. All told, Mike’s $8-a-pop hits would rake in $400 million in the first year alone, he figures.

Bloomberg is right that road fees could deter some cost-conscious drivers and help ease traffic jams. In theory, at least. In practice, there are considerable challenges.

In any event, it sure would be nice if the mayor remembered his newfound fondness for free markets when it comes to housing, taxis or other price-capped items.

Let’s face it: This town suffers from no shortage of shortages. Gothamites would kill for more cheap apartments and fewer waits for cabs. Good theater and sporting-event tickets are often impossible to come by.

These shortages have something in common: artificially low prices – capped either by Big Government or, as in the case of tickets, by the sellers themselves.

Housing and taxi fares are subject to regulation. Ticket prices are kept below market rate, supposedly, so that working stiffs can afford them. The result? Shortages.

Demand consistently exceeds supply, as anyone who’s taken Economics 101 could have predicted. (Americans learned this the hard way when gas-price controls triggered huge lines and odd/even-day rationing during the ’70s.)

Rent caps have led tenants to “overuse” housing: No need to live outside Manhattan. No need to give up that pied-a-terre or spacious three-bedroom, even after the kids move out. With rent-regulated leases, keeping the landlord at bay is a cinch.

Capped rents also have discouraged investors from building low-priced units. And many buildings have gone condo or coop, limiting the rental stock further. No wonder it’s so hard to find an affordable rental.

Yet New Yorkers scream bloody murder when someone suggests lifting the caps. Last fall, Bloomberg himself signed legislation to extend the city’s rent-stabilization law for three more years. Albany’s modest phase-out of rent regs for upscale apartments and well-off tenants is also under attack: This month, The Post’s Ken Lovett reported that Gov. Spitzer is advancing legislation to roll back even that baby reform.

The story’s not much different for crowded streets. As Bloomberg seems to understand, when Midtown’s limited roads are “free,” they’re quickly “overused” – just as housing is soon depleted when rents are below market.

Mike believes his $8 “user fee” would, in effect, ration road use – making streets available only to those willing to pay for this precious commodity.

That makes sense. And, again, it’s nice to see Mayor Mike – who made billions in the free market – offer a nod to the merits of a capitalistic approach.

Bloomberg’s plan faces tough challenges. For starters, you can’t put toll booths in the middle of Manhattan, so he’ll need a sophisticated technological system to figure out who owes what and to make sure they pay.

A second problem: outer-borough opposition that’s so fierce the idea seemed DOA from the start. Remember, seven out of eight Gothamites live outside Manhattan and would be subject to the full fee. Many of those drivers won’t ditch their cars for subways or buses no matter what it costs.

In fact, they just might ditch New York instead.

Which raises a third problem: The additional cost of living – and doing business – in the city posed by road fees could be a tipping point, sending many residents and businesses straight out of state. That could be offset by tax cuts, but Bloomberg isn’t poised to take that route.

At this point, Mike’s plan doesn’t seem likely to overcome such sizable roadblocks.

But if the exercise leaves him with a new appreciation for free-market pricing – in such areas as, say, housing – it may yet prove useful.